FIG 1.

Examples of microbial iron mats in the vicinity of TFS (A to D) and photomicrographs of iron mat communities (E to G). (A) Iron microbial mat associated with a seep along the bank of the Kuparuk River. (B) Wet sedge meadow dominated by the cottongrass Eriophorum angustifolium. (C) Small pool or pothole. (D) Small pond with iron oxides on sediment. (E) Mat dominated by sheaths of L. ochracea. (F) Mat dominated by helical stalks reminiscent of Gallionella species. (G) Mixed morphotypes, with arrows denoting capsular oxides, indicating the possible presence of Siderocapsa species. Scale bars = 5 μm.